Which halogen among the following exists only -1 oxidation state?

Options

A. F
B. Cl
C. Br
D. I

Answer

To determine which halogen exists only in the -1 oxidation state, we can analyze the halogens: fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

### Step-by-Step Solution:

1. **Identify the Halogens**: The halogens are a group of elements in Group 17 of the periodic table, which includes fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

2. **Understand Oxidation States**: The oxidation state of an element indicates the degree of oxidation (loss of electrons) of that element in a compound. Halogens typically exhibit a range of oxidation states.

3. **Examine Fluorine**: Fluorine is the most electronegative element, meaning it has a strong tendency to attract electrons. It has 7 valence electrons and can gain 1 electron to achieve a stable octet configuration, resulting in a -1 oxidation state (F⁻).

4. **Examine Other Halogens**:
- **Chlorine (Cl)**: Chlorine can exhibit multiple oxidation states, including -1, 0, +1, +3, +5, and +7.
- **Bromine (Br)**: Bromine can also show various oxidation states, including -1, 0, +1, +3, +5, and +7.
- **Iodine (I)**: Iodine similarly can exist in multiple oxidation states, including -1, 0, +1, +3, +5, and +7.

5. **Conclusion**: Among the halogens, only fluorine consistently exists in the -1 oxidation state. Chlorine, bromine, and iodine can exhibit higher oxidation states due to the presence of d-orbitals in their electronic configuration.

### Final Answer:
Fluorine (F) is the halogen that exists only in the -1 oxidation state.